The present invention relates to a new and improved construction of pipe coupling of the type comprising a housing which can be clamped about pipe ends of pipes which are to be interconnected, there being enclosed within such housing an inwardly open sealing gasket of substantially C-shaped axial cross-sectional configuration, both of the end faces or sides of which are supported at the outer jacket surface of a respective substantially truncated cone-shaped clamping ring retained at its outer periphery in axial direction in the housing and engaging by means of claws with the periphery of the pipe ends.
In German patent publication No. 24 28 101 there is taught such type pipe coupling. It is suitable for readily interconnecting unprocessed, that is to say, simply cut-to-length pipes, regardless of the material from which they are formed, without any further preparatory or post-work. While with the prior art pipe coupling there is provided directly after clamping of the housing about the pipe ends to be interconnected a faultless sealed connection between such pipe ends, even before the pipes are subjected to internal pressure, nonetheless it has been found that this state-of-the-art pipe coupling in certain cases, with the housing only fixedly clamped but not yet back-loading of the pipes, only provides in axial direction a force-locking connection. This is so because the claws of the clamping rings, during tightening of the housing (depending upon the material from which the pipes are formed), do not yet sufficiently dig into the jacket or outer surface of the pipes.
In other words with the heretofore known pipe coupling the aperture angle of the truncated cone-shaped clamping rings is initially reduced. First then when the pipes are exposed to an internal pressure, which also acts through the pipe joint upon the inside of the gasket, is there an increase of the contact pressure of its end faces at the outer jacket surface of the clamping rings (which are axially retained in the housing), so that such first then, while increasing its aperture angle, sufficiently digs or penetrates by means of its claws into the jacket surface of the interconnected pipes. Only upon the presence of an internal pressure in the pipes does the prior art pipe coupling also provide a connection comparable to a form-locking connection also in the axial direction. This holds true in all cases where an appreciable axial load of the pipe connection first arises in the presence of internal pressure, in another words, for instance, in the case of shorter pipe conduits and those whose individual pipe sections are held by additional means, such as pipe clamps and the like.
On the other hand, in the case of longer pipe conduits it is hardly possible to prevent for instance axial loads at connection locations which have already been equipped with a clamped or tightened coupling when there does not prevail any internal pressure or at times when internal pressure is absent. This is the case for instance during the assembly of longer pipe conduits, but also when the pipe conduits are without pressure for a period of time due to thermal expansion of the pipes.
An axial load in the case of a pipe coupling which engages only in a force-locking or frictional manner however leads to an axial displacement of the one and/or the other pipe end with respect to the pipe coupling. This axial displacement or shifting is not only undesirable, but brings with it, especially with very rough outer surfaces of the pipes, the risks that with the prior art pipe coupling the sealing lips formed at the ends of the C-shaped sealing gasket will be damaged, for instance abraded, so that the sealing capability thereof is impaired.